Messages in this thread | | | From | pedward@webcom ... | Subject | Re: linux 2.0 PTE bug (fwd) | Date | Thu, 28 May 1998 11:19:18 -0700 (PDT) |
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Phil forwarded the original post of this to l-k earlier, I'm now forwarding the response I posted to BUGTRAQ.
--Perry
> > > > > Hi all, > > > > there is the program : > > [SNIP of wonderful reason to set rlimits] > > > > > The idea is to take a lot of memory. So, we map all our virtual pages, > > to force the system to allow all the pte (am talking about PC box). > > So, the process will have allocated 768 pages that will never be > > swapped (that's the crucial point). > > > > So, that's simple, you run this program as much time as you need to take > > all the memory, and the PC won't be usable anymore (for my 64Mb box, > > i need to run it about 20 times). > > > > And then, you can have a wonderful light-show with your HD-led :) (PC will > > spend its time in swapping). > > > > How to solve it ? > > Well, we could swap the pgd / pmd / pte, but i really don't know > > if it is possible or what. > > The default TASK_SIZE is set in /usr/src/linux/include/asm/processor.h it is the > virtual memory maximum map size. This in itself is not dynamically configurable > (it really has nothing to do with resources). The main factor is RLIMIT_AS, > defined in /usr/src/linux/include/asm/resource.h, it controls how much virtual > memory that a process can map, mmap utilizes virtual memory. You can > safely throttle people by running a program which calls setrlimit(2) with > RLIMIT_AS as the resource. By far, 3GB is too much. > > This is only a DoS if you LET it be a DoS. > > > > > If this bug is already well know, am sorry to disturb with it. > > > > It applies only on the 2.0 kernel, for the 2.1 (soon 2.2) i don't know > > if it works, will have to read the source. > > > > Sed. > > p6mip300@infop6.cicrp.jussieu.fr. > > > > > > --Perry >
-- Perry Harrington System Software Engineer zelur xuniL () http://www.webcom.com perry.harrington@webcom.com Think Blue. /\
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